add checksum support to apt::keyring

[milad-zanganeh]

Summary

This PR adds support for the checksum and checksum_value parameters to the apt::keyring defined type and passes them through to the underlying file resource.

The changes include:

• Adding checksum and checksum_value parameters.
• Documenting the new parameters.
• Passing both parameters to the managed file resource.
• Adding unit tests for the default behavior, custom values, and parameter validation.

Additional Context

This change allows users to specify a checksum when managing keyring files. This is useful in cases where the remote key is republished without any content changes, causing Puppet to replace the file on every run.

• Root cause and the steps to reproduce. (If applicable)
  • Some repositories republish their keyring files without changing the content, but with different metadata. As a result, Puppet continuously detects changes and replaces the file on every run.
• Thought process behind the implementation.
  • Expose Puppet's existing checksum and checksum_value parameters through apt::keyring instead of introducing custom logic, keeping the implementation simple and consistent with the underlying file resource.

Related Issues (if any)

Fixes: #1196

Checklist

• 🟢 Spec tests.
• 🟢 Acceptance tests.
• Manually verified. (For example puppet apply)

[jst-cyr]

Thank you @milad-zanganeh for the PR! I have approved the CI to run. It will run the unit tests, but acceptance testing will require the engineering team to do a fork. I'll make sure this gets on the list of work to be reviewed by engineering.